Method of forming a composite substrate

ABSTRACT

In a method according to embodiments of the invention, a III-nitride layer is grown on a growth substrate. The III-nitride layer is connected to a host substrate. The growth substrate is removed. The growth substrate is a non-III-nitride material. The growth substrate has an in-plane lattice constant a substrate . The III-nitride layer has a bulk lattice constant a layer . In some embodiments, [(|a substrate −a layer |)/a substrate ]*100% is no more than 1%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/877,549, filed Apr. 3, 2013, and titled “METHOD OF FORMING ACOMPOSITE SUBSTRATE”, which is a §371 application of InternationalApplication No. PCT/IB2011/054770, filed Oct. 26, 2011, which claimspriority to U.S. Provisional Application No. 61/409,153, Nov. 2, 2010.U.S. patent application Ser. No. 13/877,549, International ApplicationNo. PCT/IB2011/054770, and U.S. Provisional Application No. 61/409,153are incorporated herein.

BACKGROUND

Field of Invention

The present invention relates to a method of forming a compositesubstrate. A semiconductor light emitting device such as a III-nitridelight emitting device may be grown on the composite substrate.

Description of Related Art

Semiconductor light-emitting devices including light emitting diodes(LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavitylaser diodes (VCSELs), and edge emitting lasers are among the mostefficient light sources currently available. Materials systems currentlyof interest in the manufacture of high-brightness light emitting devicescapable of operation across the visible spectrum include Group III-Vsemiconductors, particularly binary, ternary, and quaternary alloys ofgallium, aluminum, indium, and nitrogen, also referred to as III-nitridematerials. Typically, III-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a sapphire, silicon carbide,III-nitride, or other suitable substrate by metal-organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxialtechniques. The stack often includes one or more n-type layers dopedwith, for example, Si, formed over the substrate, one or more lightemitting layers in an active region formed over the n-type layer orlayers, and one or more p-type layers doped with, for example, Mg,formed over the active region. Electrical contacts are formed on the n-and p-type regions.

FIG. 1 illustrates a composite substrate for growing a III-nitridestructure, described in more detail in US 2007/0072324, which isincorporated herein by reference. Substrate 10 includes a host substrate12, a seed layer 16, and a bonding layer 14 that bonds host 12 to seed16. Host layer 12 may be, for example, sapphire or Si and bonding layer14 may be, for example, SiO_(x) or SiN_(x). Seed layer 16 may be, forexample, an InGaN layer grown strained on a conventional substrate suchas sapphire, then bonded to a host 12 and released during the processfrom the growth substrate such that the InGaN seed layer at leastpartially relaxes. Providing the seed layer as stripes or a grid overbonding layer 14, rather than as a single interrupted layer, may resultin further strain relief. For example, seed layer 16 may be formed as asingle uninterrupted layer, then removed in places, for example byforming trenches, to provide strain relief.

III-nitride seed layer materials may require additional bonding steps inorder to form a composite substrate with a III-nitride seed layer in adesired orientation. Wurtzite III-nitride layers grown on c-planesapphire or c-plane SiC growth substrates are typically grown with ac-plane orientation; e.g. the so-called “c-planes” of the III-nitridelayers and the substrates are parallel to each other. Such c-planewurtzite III-nitride structures have a gallium face and a nitrogen face.III-nitrides are well known to grow with the highest crystalline quality(as measured by luminescence efficiency) when the top surface of thegrown layer is the group-III face, often referred to for economy oflanguage as the “gallium face” or “Ga-face,” even though it need notinclude gallium. The bottom surface (the surface adjacent to the growthsubstrate) is the nitrogen face or “N-face”. For example, Masui, et al.describe in “Luminescence Characteristics of N-Polar GaN and InGaN FilmsGrown by Metal Organic Chemical Vapor Deposition”, Japanese Journal ofApplied Physics 48, 071003 (2009) that the luminescence efficiency ofN-face InGaN films grown by metal-organic chemical vapor deposition(MOCVD) is less than the luminescence efficiency of Ga-face InGaN filmsgrown by MOCVD. Simply growing seed layer material conventionally onsapphire or SiC then connecting the seed layer material to a host andremoving the growth substrate would result in a composite substrate witha III-nitride seed layer with the nitrogen face exposed. III-nitridespreferentially grow on the gallium face, i.e. with the gallium face asthe top surface, thus growth on the nitrogen face may undesirablyintroduce defects into the crystal, or result in poor quality materialas the crystal orientation switches from an orientation with thenitrogen face as the top surface to an orientation with the gallium faceas the top surface.

To form a composite substrate with a III-nitride seed layer with thegallium face as the top surface, seed layer material may be grownconventionally on a growth substrate, then bonded to any suitableintermediate substrate, then separated from the growth substrate, suchthat the seed layer material is bonded to the intermediate substratethrough the gallium face, leaving the nitrogen face exposed by removalof the growth substrate. The nitrogen face of the seed layer material isthen bonded to a host substrate 12, the host substrate of the compositesubstrate. After bonding to the host substrate, the intermediatesubstrate is removed by a technique appropriate to the growth substrate.In the final composite substrate, the nitrogen face of the seed layermaterial 16 is bonded to host substrate 12 through optional bondinglayer 14, such that the gallium face of III-nitride seed layer 16 isexposed for growth of epitaxial device layers.

SUMMARY

It is an object of the invention to provide a composite substrate with aIII-nitride seed layer.

In a method according to embodiments of the invention, a III-nitridelayer is grown on a growth substrate. The III-nitride layer is connectedto a host substrate. The growth substrate is removed. The growthsubstrate is a non-III-nitride material. The growth substrate has anin-plane lattice constant a_(substrate). The III-nitride layer has abulk lattice constant a_(layer). In some embodiments,[(|a_(substrate)−a_(layer)|)/a_(substrate)]*100% is no more than 1%.

In some embodiments, since the seed layer is closely lattice matched tothe growth substrate, trenches are not required to form a relaxed seedlayer. In addition, in some embodiments the seed layer can be grown withthe nitrogen face as the top surface, so two bonding steps are notrequired to form a composite substrate with the gallium face as thesurface on which a device structure is grown. The composite substratesdescribed herein may be used as growth substrates for III-nitride lightemitting devices. III-nitride light emitting devices grown on compositesubstrates formed according to embodiments of the invention may haveless strain in the light emitting region than conventionally grownIII-nitride light emitting devices, and may therefore exhibit betterperformance than conventionally grown III-nitride light emittingdevices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art composite substrate.

FIG. 2 illustrates a III-nitride seed layer grown on a substrate.

FIG. 3 illustrates a III-nitride seed layer bonded to a host substrate.

FIG. 4 illustrates a composite substrate including a III-nitride seedlayer.

FIG. 5 illustrates a III-nitride device structure grown on the compositesubstrate of FIG. 4.

FIG. 6 illustrates a thin film flip chip light emitting device.

FIG. 7 illustrates a vertical light emitting device.

DETAILED DESCRIPTION

In the composite substrate illustrated in FIG. 1, when a strainedIII-nitride seed layer is released from the growth substrate and causedto relax, typically there is so much strain in the seed layer that aplanar seed layer buckles. Trenches may be formed in the seed layer todivide the seed layer into islands smaller than the buckling wavelength.The islands relax without buckling, but forming the trenches requiresadditional processing steps. In addition, the step of growing aIII-nitride structure on islands of seed layers requires eithercoalescing the III-nitride film over multiple islands, which is timeconsuming, or growing individual islands of III-nitride material, whichreduces flexibility in device design.

In addition, bonding the seed layer twice, first to an intermediatesubstrate, then to the host substrate, in order to form a compositesubstrate where the III-nitride material is grown on the gallium face ofthe seed layer, requires additional processing steps and increases thelikelihood of contamination of the seed layer, which may reduce yieldsor cause device failure.

In embodiments of the invention, a composite substrate includes aIII-nitride seed layer attached to a host through an optional bondinglayer. The seed layer is grown on a substrate which is lattice matched(or nearly so) to the desired III-nitride seed layer and of the samehexagonal symmetry as the III-nitride seed layer. Since the substrate islattice matched, strain in the seed layer is reduced or eliminated,thereby improving the crystalline quality of the seed layer and anylayers epitaxially deposited upon it. In some embodiments, the seedlayer is grown on the substrate with the nitrogen face exposed, suchthat only one bonding step is required to form a composite substratewhere a III-nitride structure may be grown on the gallium face of theseed layer.

FIG. 2 illustrates a seed layer 32 grown on a growth substrate 30according to embodiments of the invention. A semiconductor layer may becharacterized by a bulk lattice constant and an in-plane latticeconstant. The bulk lattice constant is the lattice constant of atheoretical, fully-relaxed layer of the same composition as thesemiconductor layer. The in-plane lattice constant is the latticeconstant of the semiconductor layer as grown. If the semiconductor layeris strained, the bulk lattice constant is different from the in-planelattice constant. Growth substrate 30 may be a non-III-nitride materialwith an in-plane lattice constant within 1% of the bulk lattice constantof the deposited seed layer 32 in some embodiments, and within 0.5% ofthe bulk lattice constant of the deposited seed layer 32 in someembodiments. In other words,[(|a_(substrate)−a_(seed)|)/a_(substrate)]*100% is no more than 1% insome embodiments, and no more than 0.5% in some embodiments. Forpurposes of embodiments of the present invention, the bulk latticeconstant of a ternary or quaternary AlInGaN layer may be estimatedaccording Vegard's law, which for Al_(x)In_(y)Ga_(z)N may be expressedas a_(AlInGaN)=X(a_(AlN))+y(a_(InN))+z(a_(GaN)), where the variable “a”refers to the bulk a-lattice constant of each binary material andx+y+z=1. AlN has a bulk lattice constant of 3.111 Å, InN has a bulklattice constant of 3.544 Å, and GaN has a bulk lattice constant of3.1885 Å.

In some embodiments, growth substrate 30 has similar or the samehexagonal basal plane symmetry as the seed layer 32. In someembodiments, growth substrate 30 is substantially impervious to attackby the chemical and thermal environment experienced during thedeposition of the seed layer 32. In some embodiments, growth substrate30 has an in-plane coefficient of thermal expansion within 30% of thatof the deposited seed layer 32. In some embodiments, growth substrate 30may or may not be transparent to near-UV radiation. In some embodiments,growth substrate 30 is a single crystal or substantially single crystalmaterial.

In some embodiments, growth substrate 30 is a material of generalcomposition RAO₃(MO)_(n), where R is a trivalent cation, often selectedfrom Sc, In, Y, and the lanthanides (atomic number 57-71); A is also atrivalent cation, often selected from Fe (III), Ga, and Al; M is adivalent cation, often selected from Mg, Mn, Fe (II), Co, Cu, Zn and Cd;and n is an integer ≧1. In some embodiments, n≦9 and in someembodiments, n≦3. In some embodiments, RAMO₄ (i.e., n=1) compounds areof the YbFe₂O₄ structure type, and RAO₃(MO)_(n) (n≧2) compounds are ofthe InFeO₃(ZnO)_(n) structure type.

Examples of suitable materials for growth substrate 30 and alattice-matched InGaN seed layer 32 are listed below:

Lattice constant y in lattice-matched Material a (Å) AppearanceAl_(x)In_(y)Ga_(1−x−y)N, x = 0 InFeZn₂O₅ 3.309 Brown 0.34 InFeZn₈O₁₁3.276 Brown 0.25 ScGaMgO₄ 3.272 Transparent 0.24 ScAlMgO₄ 3.236Transparent 0.14 InAlMgO₄ 3.29 Transparent 0.29 ScAlMnO₄ 3.26Transparent 0.20 InFeMnO₄ 3.356 Brown 0.48 InAlMnO₄ 3.319 Black 0.37InAlCoO₄ 3.301 Black 0.32 InGaFeO₄ 3.313 Black 0.36

These and related substrate materials are described in detail byKimizuka and Mohri in “Structural Classification of RAO₃(MO)_(n).Compounds (R=Sc, In, Y, or Lanthanides; A=Fe(III), Ga, Cr, or Al;M=Divalent Cation; n=1-11)”, published in Journal of Solid StateChemistry 78, 98 (1989), which is incorporated herein by reference.

In some embodiments, seed layer 32 is grown on a surface of growthsubstrate 30 that is “miscut” or angled relative to a majorcrystallographic plane of the substrate. In some embodiments, thesurface of growth substrate 30 on which seed layer 32 is grown may beoriented between −10 and +10 degrees away from the basal (0001) plane.In some embodiments, miscuts between −0.15 and +0.15 degrees tilted fromthe (0001) plane may result in large atomic terraces on the substratesurface that may desirably reduce the number of defects formed atterrace edges.

Seed layer 32 may be deposited on growth substrate 30 by any of themeans known in the art, including, for example, MOCVD, hydride vaporphase epitaxy (HVPE), or MBE. Perfect lattice matching between the seedlayer 32 and the growth substrate 30 is not necessary, although alattice match within 0.1% may permit the deposition of high-quality seedlayers 32 at least 50 μm thick. Seed layer 32 may have a thicknessbetween 100 nm and 5 μm in some embodiments, and between 100 nm and 500nm in some embodiments.

Seed layer 32 is grown on substrate 30 such that the nitrogen-face ofthe seed layer is the growth surface and the gallium-face of the seedlayer is adjacent the substrate 30 surface. The surface of substrate 30may be treated prior to deposition of the seed layer, for example toimprove the surface or for any other purpose, for example by exposingthe substrate for two minutes to a gaseous mixture of NH₃ and N₂ in aration of 2:1 at a temperature of 900° C. and a pressure of 200 mbar.

Seed layer 32 may be any material on which a III-nitride devicestructure may be grown. Seed layer 32 is often a ternary (such as InGaNor AlGaN) or quaternary (such as AlInGaN) alloy of III-nitride or otherIII-V material. The fraction of InN in an InGaN seed layer 32 may bebetween 6% and 48% in some embodiments. The Al_(x)In_(y)Ga_(z)N alloywith x˜0 has a range of energy gaps which produce light across theentire visible radiation spectrum. Consequently, all of the possiblealloy compositions can be useful in light-emitting devices such as LEDs.

In some embodiments, a zone of weakness 34 is disposed within the growthsubstrate 30 or at the substrate/seed layer interface. The zone ofweakness may be provided before or after the growth of the seed layer.In some embodiments, zone of weakness 34 is formed by implanting H or N,alone or in combination with other ions, in sufficient concentrationsuch that, upon application of heat, the ions will form microcavitieswithin the growth substrate 30. For example, H may be implanted with adose of 10¹⁷ cm⁻² with an accelerating voltage of 120 keV. In someembodiments, a zone of weakness 34 is formed by exposing the wafer witha pattern of tightly focused, pulsed laser beams of sufficient intensityand photon energy to create a plurality of micron-scale crystal defectsor voids in the crystalline structure. The pattern of crystal damage maybe generated by rastering one or more laser beams across the wafer orthe use of diffractive optics to generate a large number of spots from asingle high power laser such as an excimer laser. The laser beams may bestrongly converging with a short sub-microsecond pulse, and may createhighly localized damage.

As illustrated in FIG. 3, a bonding layer 36 may be provided bydepositing a film of SiO_(x), SiO₂, or SiN_(x) on the seed layer 32 byany of the means known in the art such as plasma-enhanced chemical vapordeposition (PECVD) or low-pressure chemical vapor deposition (LPCVD).The SiO₂ film may have a thickness of 10 nm to 10 μm in some embodimentsand 200 nm to 1 μm in some embodiments. The SiO₂ film may optionally beplanarized by chemo-mechanical polishing with, for example, a slurry ofcolloidal silica.

Seed layer 32 is bonded to a host substrate 38 through bonding layer 36,for example by pressing the growth substrate 30 and host substrate 38together at elevated temperature and/or pressure. Host substrate 38 maybe any suitable material, including but not limited to single crystal orpolycrystalline sapphire, sintered AlN, Si, SiC, GaAs, single crystal orceramic Y₃Al₅O₁₂, which may or may not be doped with activating dopantssuch as Ce such that it is wavelength converting, and metals such as Mo.

As illustrated in FIG. 4, the substrate is removed from seed layer 32 byany suitable method. In structures including a zone of weakness, thegrowth substrate 30 may be removed at the zone of weakness, for exampleby heating to activate the implanted layer described above. In someembodiments, a structure including a zone of weakness of implanted Hatoms is heated to a temperature of 600° C. (the temperature may behigher or lower, depending on the implant species and dose), whereuponthe H atoms collect into microcavities which cause the zone of weaknessto mechanically fracture. An advantage of providing a zone of weakness34 to remove the growth substrate 30 from seed layer 32 is that theremaining portion of the substrate may be polished and used again as agrowth substrate.

Other methods of removing growth substrate 30 include mechanical methodssuch as mechanical grinding, applying a rotational force between thesubstrate and the seed layer, attaching an adhesive-coated plastic filmto the substrate and a second adhesive-coated plastic film to thestructure including the seed layer and pulling the substrate and seedlayer apart, using a sharp blade to break the interface between thesubstrate and the seed layer, using a pulse of sonic energy orinhomogeneous temperature distribution to break the interface betweenthe substrate and the seed layer, applying one or more laser pulsesfocused to a small point (<1 mm²) at the interfacial plane creating ashockwave that initiates fracture, and applying a temperature gradientacross the surface normal of the seed layer and substrate (for example,higher temperature applied to one face of the seed layer, and lowertemperature applied to one face of the substrate), such that thethermally induced stress in the plane of the seed layer/substrateinterface is sufficient to cause fracture of that interface.

In some embodiments, growth substrate 30 is transparent, allowing seedlayer 32 to be removed by laser lift-off, where a laser beam is directedthrough the substrate. The layer of III-nitride material grown first ongrowth substrate 30 absorbs the laser light and melts, releasing seedlayer 32 from the substrate. Laser lift-off may be facilitated by anoptional layer of narrower-energy-gap alloy semiconductor interposingthe seed layer 32 and the growth substrate 30. The composition of thenarrower-energy-gap layer may be selected such that it absorbs more ofthe incident laser light than the seed layer 32, which may reduce theincident flux required and producing less distributed damage throughoutthe seed layer 32.

In some embodiments, all or a part of growth substrate 30, such as aportion of growth substrate 30 remaining after activating an implantedlayer to detach the substrate from the seed layer, is removed byetching, such as wet chemical etching. For example, ScMgAlO₄ is readilyattacked by aqueous mixtures of H₃PO₄ and H₂O₂, H₂SO₄:H₂O₂:H₂O, andaqueous mixtures of HF, as reported by C. D. Brandle, et al. in “Dry andWet Etching of ScMgAlO₄” published in Solid-State Electronics, 42, 467(1998), which is incorporated herein by reference. In some embodiments,all or part of growth substrate 30 is removed by reactive ion etchingusing a gaseous mixture of Cl₂ and Ar at an applied power of 800 Watts.

In some embodiments, seed layer 32 is bonded to host substrate 38through bonding layer 36 such that the group III or gallium face of thewurtzite crystal is the top surface 32 a of seed layer 32, the surfaceavailable for growing III-nitride or other semiconductor material. Thegroup V or nitrogen face of the wurtzite crystal is the bottom surface32 b of seed layer, the surface adjacent to bonding layer 36.

A semiconductor device structure 22 may be grown on seed layer 32 of thecomposite substrate, as illustrated in FIG. 5. Though in the examplesbelow the semiconductor device structure is a III-nitride LED that emitsvisible or UV light other device such as electronic and optoelectronicdevices such as laser diodes, high electron mobility transistors, andheterojunction bipolar transistors may be formed on the substratesdescribed herein.

As illustrated in FIG. 5, a semiconductor structure 22 is grown overseed layer 32. The semiconductor structure 22 includes a light emittingor active region 23 sandwiched between n- and p-type regions 21 and 25.An n-type region 21 is typically grown first and may include multiplelayers of different compositions and dopant concentration including, forexample, preparation layers such as buffer layers or nucleation layers,which may be n-type or not intentionally doped, and n- or even p-typedevice layers designed for particular optical or electrical propertiesdesirable for the light emitting region to efficiently emit light. Then-type region 21 is between 1 and 20 μm thick in some embodiments andbetween 1 and 5 μm thick in some embodiments. A light emitting or activeregion 23 is grown over the n-type region 21. Examples of suitable lightemitting regions 23 include a single thick or thin light emitting layer,or a multiple quantum well light emitting region including multiple thinor thick light emitting layers separated by barrier layers. The activeregion 23 is between 1 nm and 5 μm thick in some embodiments, between 2nm and 1 μm thick in some embodiments, and between 5 nm and 100 nm thickin some embodiments. A p-type region 25 is grown over the light emittingregion 23. Like the n-type region 21, the p-type region 25 may includemultiple layers of different composition, thickness, and dopantconcentration, including layers that are not intentionally doped, orn-type layers. The p-type region 25 is between 100 nm and 2 μm thick insome embodiments and between 20 nm and 400 nm thick in some embodiments.

In some embodiments, the light emitting layer or layers in the lightemitting region 23 have a composition that is nearly lattice matched tothe seed layer (which is in turn lattice-matched to the growth substrate30). Strain in a light emitting layer is defined as[(|a_(bulk)−a_(in-plane)|)/a_(bulk)]*100% , where awn, is the latticeconstant of a layer of the same composition as the light emitting layerwhen fully relaxed, which is estimated according to Vegard's law, anda_(in-plane) is the lattice constant of the light emitting layer asgrown in the device. Strain in at least one of the light emitting layersis less than 1% in some embodiments, less than 0.5% in some embodiments,and less than 0.1% in some embodiments. In one embodiment, ScMgAlO₄ isthe growth substrate 30 and the n-type, light-emitting, and p-typelayers are formed of In_(0.13)Ga_(0.87)N, In_(0.16)Ga_(0.84)N, andIn_(0.12)Ga_(0.88)N respectively. The seed layer is the same compositionas the n-type region, In_(0.13)Ga_(0.87)N.

The structure illustrated in FIG. 5 may be processed into any suitabledevice design, including but not limited to the thin film flip chipdevice illustrated in FIG. 6 and the vertical device illustrated in FIG.7.

In the device illustrated in FIG. 6, p-contact metal 26 is disposed onthe p-type region 25, then portions of the p-type region 25 and activeregion 23 are etched away to expose an n-type layer for metallization.The p-contacts 26 and n-contacts 24 are on the same side of the device.P-contacts 26 are electrically isolated from n-contacts 24 by gaps 27,which may be filled with an electrically insulating material such as adielectric. As illustrated in FIG. 6, p-contacts 26 may be disposedbetween multiple n-contact regions 24, though this is not necessary. Insome embodiments either or both the n-contact 24 and the p-contact 26are reflective and the device is mounted such that light is extractedthrough the top of the device in the orientation illustrated in FIG. 6.In some embodiments, the contacts may be limited in extent or madetransparent, and the device may be mounted such that light is extractedthrough the surface on which the contacts are formed. The semiconductorstructure is attached to a mount 28. All or part of the compositesubstrate on which semiconductor structure 22 is grown may be removed,as illustrated in FIG. 3, or may remain part of the device. For example,host substrate 38 and bonding layer 36 may be removed, and seed layer 32may remain part of the device. In some embodiments, the semiconductorlayer exposed by removing all or part of the composite substrate ispatterned or roughened, which may improve light extraction from thedevice.

In the vertical injection LED illustrated in FIG. 7, an n-contact isformed on one side of the semiconductor structure 22, and a p-contact isformed on the other side of the semiconductor structure. For example,the p-contact 26 may be formed on the p-type region 25 and the devicemay be attached to mount 28 through p-contact 26. All or a portion ofthe composite substrate may be removed and an n-contact 24 may be formedon a surface of the n-type region 21 exposed by removing all or aportion of the composite substrate. Electrical contact to the n-contactmay be made with a wire bond as illustrated in FIG. 7 or a metal bridge.

The LED may be combined with one or more wavelength converting materialssuch as phosphors, quantum dots, or dyes to create white light ormonochromatic light of other colors. All or only a portion of the lightemitted by the LED may be converted by the wavelength convertingmaterials. Unconverted light emitted by the LED may be part of the finalspectrum of light, though it need not be. Examples of commoncombinations include a blue-emitting LED combined with a yellow-emittingphosphor, a blue-emitting LED combined with green- and red-emittingphosphors, a UV-emitting LED combined with blue- and yellow-emittingphosphors, and a UV-emitting LED combined with blue-, green-, andred-emitting phosphors. Wavelength converting materials emitting othercolors of light may be added to tailor the spectrum of light emittedfrom the device.

The wavelength converting element may be, for example, a pre-formedceramic phosphor layer that is glued or bonded to the LED or spacedapart from the LED, or a powder phosphor or quantum dots disposed in anorganic encapsulant that is stenciled, screen printed, sprayed,sedimented, evaporated, sputtered, or otherwise dispensed over the LED.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. Therefore, it is not intended that the scopeof the invention be limited to the specific embodiments illustrated anddescribed.

What is being claimed is:
 1. A method comprising: growing a III-nitridelayer with a bulk lattice constant a_(layer) on a non-III-nitride growthsubstrate with an in-plane lattice constant a_(substrate) such that[(|a_(substrate)−a_(layer)|)/a_(substrate)]*100% is no more than 1%;providing a composite substrate comprising the III-nitride layer bondedto a host substrate; and growing a semiconductor structure comprising alight emitting layer disposed between an n-type region and a p-typeregion on the III-nitride layer of the composite substrate.
 2. Themethod of claim 1 wherein growing a III-nitride layer comprises growingthe III-nitride layer such that a group V face of the III-nitride layeris the growth surface and a group III face of the III-nitride layer isdisposed on the non-III-nitride growth substrate.
 3. The method of claim2 wherein growing a semiconductor structure comprises growing thesemiconductor structure on the group III face of the III-nitride layer.4. The method of claim 1 wherein the non-III-nitride growth substrate isScAlMgO₄ and the III-nitride layer is InGaN.
 5. The method of claim 1wherein the non-III-nitride growth substrate is RAO₃(MO)_(n), where R isselected from Sc, In, Y, and the lanthanides; A is selected from Fe(III), Ga, and Al; M is selected from Mg, Mn, Fe (II), Co, Cu, Zn andCd; and n is an integer ≧1.
 6. The method of claim 1 wherein theIII-nitride layer is one of InGaN and AlInGaN.
 7. The method of claim 1wherein the III-nitride layer is In_(x)Ga_(1-x)N, where 0.06≦x≦0.48. 8.The method of claim 1 wherein the composite substrate comprises anon-III-nitride bonding layer disposed between the III-nitride layer andthe host substrate.
 9. The method of claim 8 wherein the III-nitridelayer is InGaN, the bonding layer is SiO_(x), and the host substrate issapphire.
 10. The method of claim 1 further comprising removing aportion of the composite substrate after growing a semiconductorstructure.
 11. The method of claim 1 further comprising forming a metaln-contact on the n-type region and a metal p-contact on the p-typeregion, the metal n- and p-contacts formed on a surface of thesemiconductor structure opposite the composite substrate.
 12. The methodof claim 1 further comprising forming a metal n-contact on the n-typeregion and a metal p-contact on the p-type region, the metal n- andp-contacts formed on opposite surfaces of the semiconductor structure.13. The method of claim 1 wherein growing a III-nitride layer comprisesforming a zone of weakness in the growth substrate or at an interfacebetween the growth substrate and the III-nitride layer.
 14. The methodof claim 13 wherein the zone of weakness comprises a region implantedwith one of H atoms and N atoms.
 15. The method of claim 13 wherein thezone of weakness comprises a plurality of micron scale crystal defectsor voids created by irradiation with focused laser beams.
 16. The methodof claim 1 further comprising positioning a wavelength convertingmaterial in a path of light emitted by the light emitting layer.
 17. Themethod of claim 15 wherein the wavelength converting material comprisesquantum dots.